1. Field of the Invention
This invention pertains to hollow metal microcylinders produced from diacetylenic lipids by self-assembly and to a process for making same.
2. Description of Related Art
Organic tubules formed from a diacetylenic lipid by self-assembly were first publicly described in 1984 and achieved by a process of lipsomomal cooling. The lipid, i.e., 1,2-bis(10,12-tricosadiynoyll)-sn-glycero-3-phosphocholin (DC-8,9-PC), was heated in water above 50° C. and cooled. Upon cooling below the melting temperature of 42° C., the liposomes were observed to convert to tubules of sub-micron diameter by self-assembly. Later it was demonstrated how the tubules could be generated from the same lipid by the addition of water as a non-solvent to a solution of the lipid in alcohol or propylene glycol. The tubules were allowed to grow for periods up to 6 months and resulted in average lengths of up to 100 microns. Still later, the role of alcohols in tubule formation was further investigated. The lipid, i.e., DC-8,9-PC, in alcohol/water solutions, was heated to 60° C. and tubules were formed by cooling to room temperature. The solvent 85% methanol was found to yield tubules with the greatest lengths with an average of 65 microns.
Preparation of metallized derivatives from lipid tubules was reported in 1987. Permalloy-coated tubules have been used in composites to produce high-dielectric, low-loss materials by aligning the tubules with a magnetic field and similar technique was used to produce composites with significant ferromagnetic properties. The prior art tubules were not electrically conducting probably due to the fact that electroless metal plating was conducted to the point when bubbling commenced indicating that the bath was not exhausted and an insufficient amount of metal was plated on the tubules. A successful application of this technology was demonstrated in 1992 by aligning metallized tubules in a magnetic field and cast in epoxy. Subsequently, the epoxy was etched away and the surface sputter-coated with gold. This structure was used to show a very low vacuum field emission of less than 10μA.
Progress in the application of tubule technology has been held back by the non-uniformity and incompleteness of the metal coating. Further, the coating consisted in a large part of metals and metallic oxides, such as nickel and nickel oxides, rather than a metallic alloy, such as nickel alloy.